This is a national study of physicians' and nurses' (hereafter, "health care workers." or HCWs) knowledge, attitudes, risk perceptions, practices, and career plans related to AIDS. The specific aims of the the study are: 1. To describe HCWs' knowledge about AIDS (its epidemiology and transmission, precautionary guidelines, HIV antibody testing procedures), attitudes (willingness to treat, duty to treat, gay men and IV drug users, precautionary guidelines, AIDS-related policy issues-- mandatory testing, Segregated facilities for AIDS patients, contact notification), perceptions of the risk of contagion as a result of caring for AIDS patients, practices and behavior (counselling about prevention of AIDs., ordering of the HIV antibody test, "avoiding" AIDS patients, and withholding treatments and procedures), and career plans (the extent to which HCWs have thought about leaving patient care and the extent to which their thinking has been influenced by AIDS). 2. To analyze HCSs' knowledge, attitudes, risk perceptions, practices, and career plans in relation to each other. For example, are perceptions of the risk of contagion associated with attitudes toward gay men and IV drug users? 3. To analyze variation in HCWs' knowledge, attitudes, risk perceptions, practices, and career plans according to their professional characteristics (such as whether they are physicians or nurses, their specialty, and worksetting) and their social characteristics (such as their age, gender, religious, racial, and ethnic background and religiosity). 4. To analyze differences in HCWs' knowledge, attitudes, risk perceptions, practices, and career plans according to geographic area. Two sets of comparisons will be made: between San Francisco vs. New York, Newark, and Jersey City (combined); and between HCWs according to the cumulative number of AIDS cases in their state through December, 1988. Methods. Data will be collected from national samples of 1,500 physicians in "patient care" and 1.500 nurses by telephone interview and mail questionnaire, respectively. The samples will be stratified geographically.